Traditional galvano motor scanning head correction data is pre-calculated based upon the optical design parameters of the optics used within said galvano motor scanning head and is limited by several factors:
Firstly, in the case of pre-objective scanning where a flat-field or f-Theta or telecentric lens or lenses are used and because the pre-calculated or proactive galvano motor driven scanning head correction data is commonly generated by knowing the galvano motor driven deflection mirror separation distances, the galvano motor driven deflection mirror scanning angles, the final galvano motor driven mirror separation distance to said flat-field or f-Theta or telecentric lens or lenses and the design parameters of said flat-field or f-Theta or telecentric lens or lenses any pre-calculated or proactive galvano motor driven scanning head correction data will not take into account any intolerances of the beam or laser beam or galvano motor mounting or optical mounting or paralellity between the galvano motor driven scanning head and the target plane.
Secondly, in the case of post-objective scanning where an active or passive telescope comprising a series of lenses is used, and because the pre-calculated or proactive galvano motor driven scanning head correction data is commonly generated by knowing the telescope lens element design parameters and separation distances, the galvano motor driven deflection mirror separation distances, the galvano motor driven deflection mirror scanning angles, and the final galvano motor driven mirror separation distance to the target plane any pre-calculated or proactive galvano motor driven scanning head correction data will not take into account any intolerances of the beam or laser beam or galvano motor mounting or optical mounting or paralellity between the galvano motor driven scanning head and the target plane.
Third, because said process of pre-objective or post-objective galvano motor scanning head correction data is pre-calculated and hence proactive any field distortions remaining after said pre-objective or post-objective galvano motor scanning head correction data is generated and applied due to any intolerances must be further corrected by a complex process of marking, measuring and inputting fresh data into said pre-objective or post-objective galvano motor scanning head correction data to apply further corrections to perfectly match said pre-objective or post-objective galvano motor scanning head correction data to further correct for said intolerances to achieve distortion free targeting.
Fourth, because said pre-objective or post-objective galvano motor scanning head correction data is pre-calculated and hence proactive said pre-objective or post-objective galvano motor scanning head correction data must be generated knowing the design parameters of optics that optic manufacturers do not commonly wish to divulge.